    :set (-<> ch-tags
              :set
              (or #{})
-             (apply conj <> tag))})
+             (apply conj* <> tag))})
 
 (defn get-children-tag-summary*
   [zipr pred-map]

          (-<> summary
               :set
               (or #{})
               (apply conj <> tags))
          #{})})

(defn merge-children-tag-summary

  ((or *get-tags-mz* get-tags)
   node
   pred-map))

(defn conj*
  [& r]
  (if (= (count r) 1)
    (first r)
    (apply conj r)))

(defn insert-tags-into-summary
  [& [tags summary]]
